I started using CMake pretty recently. It is a really easy script language but there are many tricks to learn and tutorials on the cmake website is not much help.
Basically I want to build my project for
Dependending on the OS and plateforme I want to link certain libraries.
I figured out for Windows that I can use WIN32 or WIN64 to set this up. But I can't find the equivalence for mac os. Can someone point me in the right direction?
In addition to the "if(APPLE)" and other variables that Tobias pointed you to in his answer, you can also inspect what generator you're using to make decisions on a per-generator basis if necessary.
if(CMAKE_GENERATOR MATCHES "Xcode")
...
elseif(CMAKE_GENERATOR MATCHES "Win64")
...
endif()
On the Mac, you can build universal binaries by setting the target property OSX_ARCHITECTURES, or the variable CMAKE_OSX_ARCHITECTURES: http://cmake.org/cmake/help/cmake-2-8-docs.html#prop_tgt:OSX_ARCHITECTURES
Alternatively, you can build two single-architecture binaries using two separate build trees with a single value in CMAKE_OSX_ARCHITECTURES for each build tree.
On Windows, you should simply have two separate build trees, on for your 32-bit build and one for your 64-bit build.